1979 Cb750K "Imperfection" Cafe/Brat Build Thread

kkane97

New Member
Now that I have made some progress I figured I would start my build thread. The base is a '79 Cb750k that has a mere 8300 miles on it! I picked the bike up in NJ for $240 and figured if it doesn't go the way I want, I could always part it out for more than I have into it. This is also my first motorcycle, I have grown up around bikes all my life and now that I am 16... I know... I would like to have one I can call my own. I am doing all of the work myself with little help mechanically from my dad.

So here goes, I am going to try to keep this as updated as possible, progress is quite slow, working part time and with school starting in 2 weeks, I am hoping to be done by end September.

When I had picked up the bike, it was not running but in pretty good shape, needed a ton of care cosmetically, it sat outside for quite a while, although it was last on the road in 2005



I got it home and decided I should get it running so I know exactly what it is I am working with, I pulled the carbs and there was a little varnish in the bowls, so I did the trick with boiling in lemon juice and they cleaned right up, rebuild with new gaskets and put them back on the bike, a little starter fluid and a new battery got the bike running

In the video with my excitement I forgot to put the airbox back on so it was running a bike rough at higher rpms, I should have taken one with it back on before tear down!

http://s1190.photobucket.com/user/kkane97/media/VID_20130626_071415.mp4.html


I started to tear it down and documented absolutely everything, taking pictures and bagging parts as they came off, I got it torn to the frame in about 2 hours time







After everything was torn down, I began to sand blast it all, just a simple tarp draped on the ground let me collect most of the sand and I was able to reuse it. The frame, tank, and many other small parts where blasted to bare metal

xXwPEwB.jpg


After sand blasting I started work on the rear hoop for the bike, being cheap I did't feel like spending the money on a pipe bender, so I used a series of cuts and welds to "bend" the metal into a hoop, it came out really nice and looks great on the frame, I just attached it using slugs on the inside


After running out of argon, it always seems to happen when you need to weld :D, I put it on the bike


After than I began to paint, keep in mind I have never painted before and the whole experience was a lot of reading and trial and error, it is lightyears from perfect, but looks better than it did prior
IMG_20130723_221906.jpg

And this is the tank after wetsanding
IMG_20130728_094002.jpg

Then I started work on the new seat pan, I began by welding 3 new cross members to the frame to attach the pan
Just tacked on here


Then I made templates for the pan, I made it in 2 sections, then welded them together for my ease.

After that all that was left was to bend the sheet metal to the shape and mount it on, for mounting I am using nuts welded to the top side of the pan, it bolts on from the bottom with lock washers and loctite.



I named the bike Imperfection because I know nothing on it will be perfect, but it is my first motorcycle and I am learning as I go along, I will definitely make some changes in my methods for the next project!

on the to do list is new bearings all around, finish cleaning up the motor, paint the frame, get the seat upholstered, new exhaust, new turn signals, head light and tail light then reassembly and troubleshooting any new problems
 
Man, wish I had the motivation and dream to build a bike when I was your age. Looking forward to this build and see where it goes.
 
I did a bit more work today, started working on the foam for the seat, it is just carpet padding, honestly it works really well. I just stacked layer upon layer to build it to how I wanted it to be, it is suprisingly comfortable, although thin, but thicker than a lot of cafe seats. The goal is to have a straight line in the seat from the tank to the rear end. I should be giving it to the upholsterer to make a cover for it with the tuck and roll style ribs in the center
Here's some pics:

The finished seat pan mounted on the bike for foam mock up




First layers of foam layer out, I wasn't having much luck getting nice cuts in the foam while sizing it to the pan but at this point it doesn't matter because I have yet to trim it


Now its time to trim it all up after the glue has cured, a electric carving knife is absolutely perfect to do this step


I was able to get very nice and clean cuts with the knife




All trimmed up, I still need to work the shape a bit more, but the knife isn't good for fine cuts

This one is pretty blurry, but you can see the line from the tank back
 
Nice work, man! I'll definitely be keeping an eye on this one. I'm another young builder, or aspiring builder since my build has yet to start.
I'll soon have a cb550k to wrench on. I'm hoping to go for a brat style too. My nighthawk 250 is fun, but not a great build base. Keep up the good work!
 
Good luck with the build you have a fine start.

But you have thrown me a curved ball with this thread. I have in previous thread tried to explain the difference between the various 750 models C, F, K and Ltd. Is your bike a US model or an import as all the info I could find was that all US K models came with wire wheels and here you have one with Comstars, unless they have been retro fitted.
 
Thanks everyone for the feedback!

Notlob, the bike was completely stock as far as I know, original comstars, are you possibly finding the spoked wheels on the SOHC models? This is the first year of the DOHC models and here is a stock image of a 1979 cb750k just like this one
Honda%20cb750KZ.jpg
 
The euro K models always had comstars but according to the Honda parts diagrams the US model KZ had spoke wheels

Also that photo is it a US spec bike as it should have the side reflectors on the headlamp ears if it is.

honda-cb750k-750-four-k-1979-usa-front-wheel-cb750k_bighu0116f5z10_3ca3.gif
z
 
I agree notlob, that bike does tend to break the rules. UNLESS it was originally a '79 only LTD model. That model was basically a K styled bike with Commies and a single front disc brake and rear drum. But then your awesome tail section is all wrong... maybe just the wheels from one.

1979%20cb750k%20right%20side%20large.jpg


Fist off, your bike doesn't have the same wheels as the K model in the referance pic. It is sporting the first generation "Comstar" wheels while your bike has the later "Reversed Comstar". Take close look at the spokes. The centers are rounded with the edges turning inwards on the first years, while yours are cupped with the edges turning outwards, or "reversed" of the original design.
Next, I don't know where Tony at http://www.motorcyclespecs.co.za/ gets all that wonderful data, but I have found it not to be 100% accurate when it comes to US models. (my Suzuki L for example). Wiki says websites that end with .za are from Zambia. If that's the case, I don't know if it would be the best resource for US only models. ::)

Either way, damn nice bike and good on you for jumping in with both feet!
 
HD Now that I look at the pic of the bike that I posted the rims look nothing like mine, they are exactly like the on in the pic that you posted, I also do have to reflectors that screw into the headlight as well
 
As far as I'm concerned the Comstars are a welcome addition. Cheaper to restore and you can run tubeless tyres. Anyhow dont let us distract you from the build.
 
Hoosier Daddy said:
I agree notlob, that bike does tend to break the rules. UNLESS it was originally a '79 only LTD model. That model was basically a K styled bike with Commies and a single front disc brake and rear drum. But then your awesome tail section is all wrong... maybe just the wheels from one.

1979%20cb750k%20right%20side%20large.jpg


Fist off, your bike doesn't have the same wheels as the K model in the referance pic. It is sporting the first generation "Comstar" wheels while your bike has the later "Reversed Comstar". Take close look at the spokes. The centers are rounded with the edges turning inwards on the first years, while yours are cupped with the edges turning outwards, or "reversed" of the original design.
Next, I don't know where Tony at http://www.motorcyclespecs.co.za/ gets all that wonderful data, but I have found it not to be 100% accurate when it comes to US models. (my Suzuki L for example). Wiki says websites that end with .za are from Zambia. If that's the case, I don't know if it would be the best resource for US only models. ::)

Either way, damn nice bike and good on you for jumping in with both feet!
CO.ZA websites mean South Africa.Not Zambia.
South Africa is in worse trouble then I thought
 
Re: 1979 Cb750K Cafe/Brat Build Thread

No real updates today, just some little polishing here and there, started to clean the outside of the motor up with a scotchbrite and wd40, I decided that I am going to just wrap my existing 4-2 headers rather than buy a new set for now. I am going to get some new mufflers for them though, thinking about these from DCC
http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-exhaust-parts-12-inch-shorty-muffler-80-03310-sbpc.html
Will I need to jet my carbs with these mufflers? As of now I am running very nicely on the stock jetting for the carbs, but I am guessing that it will act differently for the new tips. I am new to carbs especially the CV carbs on the DOHC models so any help would be greatly appreciated!
 
Did a whole bunch of polishing today, sprocket covers spark advance covers, fork lowers, man do my hands hurt, everything was started from 500grit and worked up to 1500 grit, then buffed on the wheel, a lot of work but worth it, I also painted the inside of the Honda logo on the advancer cover. I will be doing the same on the clutch side
Before

After scrubbing for 10 mins with a scotchbrite

After buffing



Should be some more tomorrow
 
Some more work pics, started on the cleaning of the motor, and began wrapping the headers.
The wrap is more of a temporary "fix" until I get a new exhaust system, but for the time being it will be much better than the peeling chrome.


New Mufflers


Also got the foam for the seat finished up, ready for the upholsterer tomorrow! Going with a tuck and roll style
 
Sent the seat out today to get the truck and roll cover made up and installed, no major updates lately, mainly waiting to paint the frame to then begin reassembly. That's when the fun begins!


So far my list that I can think of is
New wheel bearings front and back,
rebuild front caliper,
new shoes on rear caliper,
mount taillight,
mock up new exhaust mounts,
Fabricate new perforated metal side covers,
 
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